Method of forming an insert bush

ABSTRACT

An insert for providing a screw-thread when pressed into soft material includes two rings connected together and having external inclined splines of opposite hand, so that in the pressing operation the two rings are contra-rotated, and can lock together. The insert is made as a one-piece construction, and is divided into two pieces which are fixed together, in a single press movement.

United States Patent [191 Tildesley METHOD OF FORMING AN INSERT BUSH[75] Inventor: John Matthew Tildesley, Wolverhampton, Staffordshire,England [73] Assignee: The Precision Screw & Manufacturing CompanyLimited, Dillenhall, England [22] Filed: May 5, 1971 [21] Appl.No.:140,538

[52] US. Cl. ..l0/86 R, 10/155 A, 151/41.73 [51] Int. Cl ..B2ld 53/24,B23p 19/08 [58] Field of Search ..10/86 R, 155 A; 29/413; 85/61;l51/41.73

[56] I References Cited UNITED STATES PATENTS 1,868,415 7/1932 Gundersenet a1 ..10/155 A Apr. 17, 1973 2,520,259 8/1950 Pummill ..85/61 X2,813,568 11/1957 2,858,602 11/1958 Johnson 3,037,221 6/1962 Lanius3,198,231 8/1965 Bisbing ..15l/41.73

Primary Examiner-Charles W. Lanham Assistarit Examiner-E. M. CombsAttorney-Marshall & Yeasting 5 7] ABSTRACT An insert for providing ascrew-thread when pressed into soft material includes two ringsconnected together and having external inclined splines of oppositehand, so that in the pressing operation the two rings arecontra-rotated, and can lock together. The insert is made as a one-piececonstruction, and is divided into two pieces which are fixed together,in a single press movement.

2 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION This inventionrelates to insert bushes adapted to provide a screw anchorage point insoft material, and

comprising a body formed with an internally screwthreaded bore, and withinclined fins or teeth on the extema] periphery of the body, so that itmay pressed by a primarily axial movement into a pilot hole formed forthe purpose in the work, and in entering into the work will be turnedangularly as the teeth out complementary recesses in the work.

Such inserts resist pull-out or axial load, due to the frictionalresistance to turning.

it has previously been proposed to provide a ring at one end of theinsert bearing teeth of the opposite hand to those on the body, so thatwhen the ring is driven into the work immediately after the insert, itwill cut teeth in the opposite direction, and then if the body tends torotate under pull-out load it will jam against the ring, and because itwill tend to rotate the ring in the direction which screws the ringfurther into the work, removal of the insert by this applied load willnot occur. However, such known inserts were inconvenient, becauseparticularly when made in smaller sizes, the correct insertion of thering was difficult.

SUMMARY OF THE INVENTION The object of the present invention is toprovide an improved insert of this kind which is particularly convenientfor insertion into workpieces. A further object of the invention is toprovide an improved method of manufacturing inserts of this kind.

In accordance with the present invention, an insert for providing ascrew-threaded anchorage point in work comprises a body formed with atleast one band of inclined teeth or fins on its outer periphery, and aring also having inclined teeth on its outer periphery, but of theopposite hand to the teeth on the body, the ring being larger indiameter than the body, and being axially captive but rotationally freeto the body.

According to another aspect of the invention, a method of making aninsert comprising a body having teeth on its periphery and a ring whichis axially captive and rotationally free to the body, comprises formingthe ring and body as a single component with a thin neck of materialtherebetween and with a shoulder provided on a face located in the spacebetween the ring and body, and displacing the ring and body relative toone another and towards one another so as to shear the two at the necktherebetween, and impact the shoulder I so as to deform materialradially inwardly so as to make the parts axially captive together.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged part sectionalelevation of an insert;

FIG. 2 is a fragmentary sectional elevation of the same on an enlargedscale, FIGS. 1 and showing the parts in a first stage of themanufacturing method to be described.

FIG. 3 illustrates an inten'nediate step in the manufactnring method,and is generally similar to FIG. 2, and

FIG. 4 is a view again similar to FIGS. 2 and 3 showing the completedinsert in one respect.

DESCRIPTION or THE PREFERRED EMBODIMENT Referring now to the drawings,the insert comprises a generally tubular body provided with a pilotsection 11 which is cylindrical apart from a leading chamfer Ila, and isof the same diameter as that of a pilot hole into which the insertsection is to be pressed. The pilot is spaced from the remainder of thebody by a neck 11b and an aligning chamfer 1 1c. The body is providedwith two lands l2 separated by a groove 14, the base of which is ofsubstantially the same diameter as the pilot section 1 l, and the lands12 are provided with helically extending fins or teeth 13 whicharealigned, and the roots of the teeth lie on the same diameter as thepilot section 11 and groove 14, or could lie on a smaller diameter.However, the groove could be deeper, so that its diameter is less thanthe root diameter of the teeth on the body. On the opposite side of thelands 12 to the pilot section 11 there is a neck 16. This portion of theneck, lands, groove and pilot section is hereinafter called the body ofthe insert and is provided with a screw threaded bore 10 therethrough.

Also provided, as an integral part of the insert during the initialstage of manufacture, is a ring 15 also provided with helicallyextending fins or teeth, but which are inclined in the oppositedirection or hand to those of the lands 12. The ring 15 is of slightlylarger diarne: te r than the lands 12 so that the roots of the teeth ofthe ring 15 lie on a diameter equal to or larger than the maximumdiameter of the lands 12. The ring 15 is bored at 22 to a diametersubstantially equal to the maximum diameter of the neck 16, see FIG. 2

The insert formed as illustrated in FIG. 1 is then axi; ally contracted,as by an impact blow on one end face while the opposite end face isagainst an abutment, so as to shear the ring in the portion 18 (see FIG.2 atthe extremity of the neck 16. As seen in FIG. 2, the ring has ashoulder 26 which is a narrow annulus raised from a face of the ring bya step 24, and this step lies in the gap 28 between iand 12 and ring 15.

FIG. 3 shows the parts as sheared, and as the axial deformationcontinues, the shoulder 26, impacts against the face 30 of the land 12which causes the material the shoulder to be deformed and flow radiallyinwards. This resu lts in the internal periphery of the ring in thevicinity of the area 18 being reduced in diameter, and due to the neck16 being of tapering configuration with a smallest diameter adjacentface: 30, the ring is thus rendered axially captive to the body, asshown for example in FIG. 4. Nevertheless the ring is free to rotate onthe body. i i 1 In installation of the insert, the pilot section 11 isen-: tered into the hole in the workpiece and the insert is pressed inan axial direction into the workpiece, causing the teeth 13 to cutcomplementary recesses or grooves in the workpiece, and this isaccompanied by a rotation of the insert relative to the work. Dependingon the material of the workpiece, shavings of material may displacedinto the grooves 14 and/or 111),, and these may improve the lockingaction of the insert the work. I

When the ring 15 is moved against the face of the workpiece as a resultof the axial movement, the teeth of ring 15 being of the oppositedirection of inclination, will cut a fresh set of grooves, complementaryto the teeth, in the work. Because the ring is of larger diameter thanthe body, these teeth will be acting in material which has not beenaffected or cut by the teeth 13 during their passage through thematerial. During this latter part of the insertion step the body willcontinue to rotate in the same direction as before, but the ring will berotating in the opposite direction.

- When the insert is pressed fully home, so that the end face of thering remote from the body is flush with the work, and a screw isinserted into the bore to clamp a component against the end face 18, thering and body become clamped together, and are prevented from turningunder pull-out loads, so that instead of relying upon frictionalresistance to turning, it is shear strength of the material (or insert)which resists pull-out. The insert therefore provides a particularlysecure hold against such loads whilst being convenient for manufactureand use.

I claim:

1. A method of fabricating an insert having a plurality of peripheralbands of teeth which are inclined to the axis of the insert, the teethof a first band at one end of the insert being of hand opposite to theteeth of a second, adjacent band, wherein the improvement comprises thesteps of (a) forming, between the first and second bands, a groovehaving a substantially frustoconical bottom, with its smallest diameteradjacent to the second band, while forming a shoulder extending from thebottom of the groove adjacent to the first band, and forming a boreextending axially through the first band which has a diametersubstantially equal to the largest diameter of the frusto-conical bottomof the groove, and (b) axially compressing the insert and therebyshearing the first band free and compressing the shoulder against thesecond band to deform the material of the shoulder radially inwardagainst the frusto-conical portion, thus anchoring the first bandagainst axial movement while leaving it free to rotate relative to thesecond band.

2. A method according to claim 1 wherein the first band of teeth isformed with a diameter greater than that of the second band of teeth,

1. A method of fabricating an insert having a plurality of peripheralbands of teeth which are inclined to the axis of the insert, the teethof a first band at one end of the insert being of hand opposite to theteeth of a second, adjacent band, wherein the improvement comprises thesteps of (a) forming, between the first and second bands, a groovehaving a substantially frustoconical bottom, with its smallest diameteradjacent to the second band, while forming a shoulder extending from thebottom of the groove adjacent to the first band, and forming a boreextending axially through the first band which has a diametersubstantially equal to the largest diameter of the frusto-conical bottomof the groove, and (b) axially compressing the insert and therebyshearing the first band free and compressing the shoulder against thesecond band to deform the material of the shoulder radially inwardagainst the frusto-conical portion, thus anchoring the first bandagainst axial movement while leaving it free to rotate relative to thesecond band.
 2. A method according to claim 1 wherein the first band ofteeth is formed with a diameter greater than that of the second band ofteeth.